The end
user, who owns and uses communications systems, often finds it hard to
get information about fiber optics aimed specifically at them. Industry
standards are written by and for manufacturers. Most training material
is written to train installation techs, the group the FOA focuses on
with its certification programs.

So the
FOA has created a special section of our website where end users can
find answers to their questions on fiber optics or even find out what
questions to ask. We think you will find this interesting and useful.
We welcome your questions and feedback.

Getting
Started In Fiber Optics

The FOA has several options to help you get started in fiber optics. These are the way to get started.

1. Introduction
One often sees articles written about fiber optic communications
networks that implies that fiber optics is "new." That is hardly the
case. The first fiber optic link was installed in Chicago in 1976. By
1980, commercial long distance links were in use and fiber optic data
links for RS-232 were available. Since that beginning, fiber has become
very commonplace - one should say dominant - in the communications
infrastructure.

If
you make a long distance call today, you are undoubtedly talking on
fiber optics, since it has replaced over 90% of all the voice circuits
for long distance communications. Most large office buildings have
fiber in the building itself. Only the last link to the home, office
and phone are not fiber and installations of fiber to the home are
growing rapidly.
CATV also has discovered fiber optics, along with compressed digital
video. Most large city CATV systems have been converted to fiber optic
backbones which allow voice and data transmission in addition to video.
The LAN backbone also has become predominately fiber-based. The
back-end of mainframes and storage area networks (SANs) are almost
totally fiber. Only the desktop is a holdout, currently a battlefield
between the copper and fiber contingents.
Fiber optics offers an unrivaled level of security. It cannot be easily
jammed or tapped and is immune to interference. It is widely used for
security cameras, perimeter alarms and other critical systems in
military, government, utility and civilian applications.
Fiber optics really is the medium of choice for long distance, high
bandwidth or secure communications. Lets look at why it is, how to
evaluate the economics of copper versus fiber and how to design fiber
networks with the best availability of options for upgradeability in
the future.

1.1
Its really all a matter of economics
Fiber optics has become widely used in telecommunications because of
its enormous bandwidth and distance advantages over copper wires.
Commercial systems today carry more phone conversations over a pair of
fibers than could be carried over thousands of copper pairs and can be
run hundreds of kilometers between all-optical repeaters. Material
costs, installation and splicing labor and reliability are all in
fiber's favor, not to mention space considerations.
In CATV, fiber pays for itself in enhanced reliability and the ability
to offer enhanced services. The enormous number of repeaters used in a
broadcast cable network are a big source of failure. CATV systems' tree
and branch architecture means and upstream failure causes failure for
all downstream users. Reliability is a big issue, since viewers are a
vocal lot if programming is interrupted! The ability to offer Internet
access has created significant revenue streams for CATV operators also.
For LAN and other datacom applications, the economics are less clear
today. For low bit rate applications over short distances, copper wire
is often a better choice. As distances go over 50 to 100 meters and
speeds above 1 Gb/s, fiber begins to look more attractive. Not only
does fiber have more bandwidth capability, but very high speed copper
links use 4-8 times more power than fiber and have latency problems.
Upgradeability usually tilts the decision to fiber, as one optical
fiber has already outlived a half-dozen generations of copper wiring.
Installing laser-optimized fiber today will provide a long useful life
to any cable plant.

Some
applications demand fiber. Factory floors are messy electrical
environments where optical fiber, both glass and plastic, are used
everywhere to provide reliable communications. Long CCTV links in
security systems are now almost exclusively fiber. Even millions of
cars use fiber (POF) for safety and entertainment/communications
systems. If reliable communications are a must, fiber is usually the
best choice.

1.2.
Technology often says go fiber
Fiber's advantages over copper result from the physics of transmitting
with photons instead of electrons. In glass, optical attenuation is
much less than the attenuation of electrical signals in copper and much
less dependent on signal frequency. We all know that fiber optic
transmission neither radiates RFI nor is susceptible to interference,
making it the only choice for secure communications. Unlike copper
wires that radiate signals capable of interfering with other electronic
equipment, fiber is totally benign. Utility companies even run power
lines with fibers imbedded in the wires for both communications and
network management!
The bandwidth/distance issue is what usually convinces the user to
switch to fiber. Although with today's applications, multimode fiber is
used at 100-1000 Mb/s for datacom applications and is usable up to 10
Gb/s. Singlemode fiber offers virtually unlimited bandwidth, especially
with DWDM (dense wavelength division multiplexing.)

2. Understanding Fiber Optic Communications
Fiber optic links are the communications pathways between devices. A
link is bidirectional, usually with signals transmitted in two
directions on two different fibers. Using two fibers is usually the
cheapest way, since the optical fiber itself is now about as cheap as
kite string and fishing line! (FTTx PON systems use one fiber in two
directions so it can use one PON coupler transmitting and receiving for
lower system cost.) The link connects electronic signals from two
devices that need to communicate, just like a copper cable. The link
has a transmitter that converts electronic signals from communications
equipment to optics and a receiver that converts the signal back to
electronics at the other end.

Fiber
optic transmitters use LEDs or semiconductor lasers to convert
electronic signals to optical signals. LEDs, similar to those used
everywhere for indicators, except transmitting in the infrared region
beyond human perception are used for slower links, up to about 100
million bits per second (Mb/s), for example fast Ethernet LANs. Faster
links use infrared semiconductor lasers because they have more
bandwidth, up to tens of billions of bits per second (Gb/s). Lasers
have more power, so they can also go longer lengths, as in outside
plant applications such as long distance telecom or CATV.
As noted, transmitters use infrared light. Infrared light has lower
loss in the fiber, allowing longer cable runs. Typically multimode
glass fibers use light at 850 nm, referred to as "short wavelength" and
singlemode fiber operates at 1310, 1470 or 1550 nm, called "long
wavelength."
Since the light being transmitted through the optical fiber is beyond
the range of human sight, you cannot look at the end of a fiber and
tell if light is present. In fact, since some links carry high power,
looking at the end of the fiber, especially with a microscope which
concentrates all the light into the eye, can be dangerous. Before
examining a fiber visually, always check with a power meter to insure
no light is present unless you know the far end of the fiber is
disconnected and use a microscope equipped with a laser filter.
At the receiver end, a photodiode converts light into electrical
current. Photodiodes must be matched to the transmitter type,
wavelength, power level and bit rate as well as the fiber size to
optimize performance. It's the receiver that ultimately determines the
performance of the link, as it needs adequate power to receive data
reliably. Receivers have a certain amount of internal noise which can
interfere with reception if the signal is low, so the power of the
optical signal at the receiver must be at a minimal level.
The power at the receiver is determined by the amount of light coupled
into the fiber by the transmitter diminished by the loss in the fiber
optic cable plant. The installer will test the cable plant for loss
after construction, comparing it to a loss calculated from typical
component values called the "loss budget." Transmitter power can be
measured when the networking equipment is installed using a patchcord
attached to the transmitter.
Networks adapt the generic fiber optic link described above to a
specific network's needs. An Ethernet link will be optimized for the
bitrate and protocol of the version of Ethernet to be used, for example
Gigabit Ethernet. Video links may be analog or digital, depending on
the camera, and may include camera controls in one direction and video
in the other. Industrial links may be based on RS-232 or RS-422
protocols.
Most computer or telecommunications networks have adopted standards for
fiber optic transmission as well as copper wiring and wireless.
However, sometimes the user has equipment with copper interfaces but
wants to use fiber. Then they can use fiber optic media converters,
which do exactly what their name suggests. Media converters will
convert from one media to another, typically UTP copper to optical
fiber, coax to optical fiber or multimode to singlemode fiber. Media
converters are like transmitters and receivers in that they must be
specified for specific network applications to insure the proper
operation in that application.
Since so many link types exist, it is impossible to generalize on fiber
optic link characteristics, but there is a
table in the FOA website detailing most standard networks.
When designing or installing fiber optic cabling, the contractor can
either design to cabling standards, which allows use with any network
or communications system designed for those standards, or for a
specific network, which may allow optimizing the cable plant. If the
actual network to use the fiber optic cabling is not known, the best
plan is to design, install and the test cable plant based on standardized
fiber optic component specifications rather than any specific
network needs.

Today,
we're seeing premises cabling, designed to carry gigabit and 10 gigabit
traffic with 850 nm VCSEL transmitters, moving toward standardization
on 50/125 laser-optimized fiber (now universally
called OM3 or OM4 for the two grades of available standardized fiber) with LC connectors
to match the manufcturers' standard for VCSEL transceivers. OM3 cabling
even has it's own color, aqua, specified in TIA-598.

If
you are planning, designing, installing or using high speed premises
fiber optic networks, it appears you should be recommending and using
OM3 or OM4 fiber and LC connectors. Within the industry, this is becoming a
"de facto" standard known as "OM3 or OM4 cabling." One big advantage of using
a full OM3 or OM4 cabling standard is that it is easily identifiable by the
aqua color and cannot be interconnected with legacy cabling.

The
FOA is encouraging all FOA-Approved schools to adopt the OM3 or OM4
nomenclature in their training. We've added this recommendation to the
FOA User's Page and will add it to the NECA/FOA 301 standard when
revised.

Here
is the "OM3 Cabling "spec for designers to use in documentation: The fiber optic cable plant will be type OM3 (or OM4)
cabling, using laser optimized (OM3 or OM4) fiber in a cable with aqua colored
jacket, terminated with LC type connectors and mating adapters all
colored acqua. Individual fiber cable runs will be specified by number
of fibers and cable type (riser, plenum, indoor-outdoor, etc.) required
by the actual installation.

3.
Checklist For Users Of Fiber Optic Communications Products
This is intended as an overview and installation checklist for all
managers and engineers on the overall process of designing, installing
and operating a fiber optic communications system. Fiber optics offers
major advantages for communications systems including security,
distance and bandwidth. Proper application of fiber optic technology
will lead to highly reliable systems. But the user must choose the
proper products, design and install an appropriate cable plant, and
make sure components are tested, all following appropriate industry
standards. This guide is designed to provide the information necessary
to ensure proper installation and usage of fiber optic systems. As
references, we will use:The FOA Online Reference Guide To Fiber Optics

Note that these documents refer to other more detailed
documents such as TIA or ISO standards.

While
this document is primarily focused on the design, installation and
maintenance of fiber optic cable plants, most end users will be
interested in costs, so the FOA has a separate document on estimation.

3.1.1.
Select a communications module or converter that fits the data format
you plan to transmit.
The first step is to choose the type of system needed. Fiber optic
communications products exist for almost every type of communications
system, from high speed telephone and CATV systems to simple low speed
RS-232 or relay closure links. Many are media converters from standard
electrical interfaces like Ethernet that have various options on data
rates. Some are proprietary links for specialty equipment used for
utility monitoring, industrial control, video surveillance, etc.

3.1.2.
Select a fiber optic product that is specified to work over the range
of your application. Note the type of fiber and other components such
as connectors required for this product.
a. Consider the range of the link as that affects the type of fiber and
transceivers needed.
b. Short links use multimode fiber and LED sources, while longer links
use lasers and singlemode fibers.
c. Most fiber optic communications products offer several versions that
cover different ranges.
d. Alternately, if you already have fiber optic cable plant installed,
select a product that will operate over your fiber optic cable plant,
considering both fiber type and distance.

3.1.3.
Select a fiber optic cable type appropriate for the application. (FOTN,
Chapters 4,5 and NECA-301, Sec 5)
a. Determine the working environment of the fiber optic cable plant.
Some applications are in office environments, some on factory floors,
above ceilings and some are outdoors.
b. Outdoors, some cables are installed aerially, either lashed to a
messenger or self-supporting, some are buried directly or in conduit
and some must run under water.
c. All outdoor cables require protection from water entry and any other
environmental factors particular to the installation.
d. Each application puts requirements on the cable design that should
be discussed with cable manufacturers who can recommend cable types
appropriate for that application.
e. Not all manufacturers make the same type of cable, so talking to
several vendors may provide options in cables that affect price or
performance.
f. Consider installing several extra fibers in case any are damaged in
installation or if additional fibers are needed for future expansion.
(In fact, for critical applications, it may be advisable to install a
complete backup link and/or redundant fiber optic cable plant run in a
different route.)
g. Often singlemode fibers are added to multimode cables (called a
hybrid cable) in case future networks need higher bandwidth.
h. At this stage, also decide on the installation hardware needed, such
as conduit or innerduct for buried cables and hangers or lashing for
aerial cables.

3.1.4.
Plan ahead on splicing requirements. (FOTN, Chapter 6 and NECA-301, Sec
6)
a. Long lengths of cables may need to be spliced, as fiber optic cable
is rarely made in lengths longer than several kilometers due to weight
and pulling friction considerations.
b. If fibers need splicing, determine how to splice the fibers (fusion
or mechanical) and what kind of hardware like splice closures are
appropriate for the application.

3.1.5.
Choose connectors of a style and termination type appropriately for the
application. (FOTN, Chapter 6 and NECA-301, Sec 6)
a. Cables will need terminations to interface with the communications
products.
b. Connectors need to be chosen appropriately or patchcords with one
end terminated with connectors compatible with the communications
products will be needed.
c. Fiber optic connectors have several termination methods, some using
adhesives and polishing, some using splicing, which have tradeoffs in
performance.
d. Discuss connectors with both manufacturers and installers before
making this choice.

3.1.6.
Ensure the calculated link loss is substantially less than the link
margin of the communications products. (FOTN, Chapter 10 and NECA-301,
Annex A)
a. Calculate the power/loss
budget for the link.
b. Using typical component specifications and the design of the cable
plant (type of fiber, length, transceiver wavelength, number of
connectors and splices) you can calculate the approximate
optical loss of the cable plant
c. Compare it to the link margin for the communications products you
have chosen.
d. Discuss potential margin problems with communications equipment
vendors.

3.2.
Install the cable plant. (FOTN, Chapters 9, 10,11, 12, 15 and NECA-301,
Sec 4 below )
a. Using the design developed in this process, install the cable plant.
b. Some users learn to install and maintain the fiber optic cable plant
themselves, while others use contractors.
c. Installers or contractors should be trained and experienced in the
installation type being done, have references for previous work and be certified
by independent organizations like The Fiber Optic Association.
d. Follow the guidelines in the NECA 301-2004 Standard For Installing
and Testing Fiber Optic Cables, available from The National Electrical
Contractors Association.
e. Do not discard excess cable from the installation, but store it for
future needs in restoration if the cable plant is damaged.

3.3.
Test the cable plant for end-to-end optical loss. (FOTN, Chapter 17 and
NECA-301, Sec 7)
a. Test
the cable plant for optical loss according to industry
standards. Most cable plants are tested according to standards
TIA/EIA-526-14 for multimode fibers and TIA/EIA-526-7 for singlemode
fibers using Method B, with a one cable reference for 0dB loss. Calculate the
approximate loss expected before you begin testing.
b. Longer cables with splices should also be tested with an OTDR to
verify splice quality.
c. Cables installed aerially or in areas of likely stress can also be
tested with the OTDR to verify installation quality.
d. Troubleshoot
any fibers that are high loss and correct the problem.

3.4.
Install the communications products and test their operation. (FOTN,
Chapter 17)
a. After the cable plant is tested and known good, install the fiber
optic communications equipment and test its operation.
b. Use any self-testing options to check operation, use BERT (bit-error
rate test) equipment or transmit known data and look for errors.
c. Once a network is operating properly, it should require no
maintenance ­ in fact, attempted maintenance on premises systems by
un-qualified personnel is often a cause of damage ­ so it is best to
lock fiber optic component enclosures to reduce unauthorized entry - a
requirement for class 4 (high power)lasers.
d. Outside plant networks may need frequent visual inspection just to
find damage or potential damage.

3.5.
Document the fiber optic network. (FOTN, Chapter 13 and NECA-301, Sec 8)
a. Perhaps the most important part of any installation is the final
documentation.
b. Accurate and complete documentation is invaluable in upgrading,
troubleshooting or restoring a network. (Download the FOA Tech
Bulleting "Fiber
Optic Restoration" PDF, 90 kB) Documentation should include
identification of all components, the paths of each cable, types of
cable (and where the excess is stored for restoration), cable section
lengths, locations of splices or terminations and the optical loss of
each fiber measured at installation.
c. If OTDR traces are taken, those should be stored with the
documentation.
d. Copies of all documentation should be kept at each end of the link
and backups stored in a safe place.

Documentation
begins with a good blueprint.

4.
Important Considerations in Fiber Optic Installation
Fiber optics offers major advantages for communications systems
including security, distance and bandwidth. Proper application of fiber
optic technology will lead to highly reliable systems. That means the
user must install an appropriate cable plant and test every component,
all following appropriate industry standards. This guide is designed to
provide to those directly involved in planning and installing the fiber
optic network the information necessary to ensure proper installation
and usage of fiber optic systems.

Notes:

Every project needs "paperwork" to define the project for both the user and the contractor. See the FOA page on Paperwork for a rundown of the important documents and what they mean.

This list only concerns itself with the project steps unique to fiber
optic systems, but many OSP applications require obtaining permits,
easements or rights-of-way. That is beyond the scope of this document!

4.1.
Do a complete design before beginning cable plant installation. (FOTN,
Chapter 9 and NECA-301)
a. Establish criteria for the install, based on the communications
paths required
b. Know how many fibers of what types are needed ­ add extras for
repairs or growth
c. Determine hardware requirements: connectors, splices, patch panels,
closures, etc.
d. Plot the cable route and determine cable lengths
e. Show how installed (premises, buried, conduit, innerduct,
underwater, pole locations for aerial, etc.)
f. Mark termination and splice points
g. Attach data from link loss budget and use it as a guide for testing
h. Don't try to build a marginal design ­ allow for "Murphy's Law"
i. Follow the NECA 301-2004 Standard For Installing and Testing Fiber
Optic Cables in design and installation
j. At the same time, design the facilities for the communications
equipment, including locations, allowing for adequate spaces, power and
grounding and HVAC as needed
k. Make complete lists of what components and hardware are needed and
where they are to be used

4.2.
Work with vendors on component specs to get best quality and price.
a. Vendors usually have suggestions on components like cables or
hardware that can facilitate design and implementation, but always get
several opinions and compare their suggestions to what you understand
you need .
b. Consider options like pre-terminated cables or air-blown fiber for
short indoor cable runs
c. Remember to plan for purchasing overages on components to cover
extra cable for restoration or extra connectors necessary due to yields
in termination
d. Be careful of industry or manufacturer "jargon" as not everyone uses
the same term in fiber optics

4.3.
Have all components available before beginning installation so crews
may complete the installation promptly and properly.
a. Inventory everything received
b. Check for shipping damage
c. Store in a safe, dry place until used
d. Separate as needed for each work site
e. While at the job site, consider using guards if components are left
onsite overnight

4.4.
Use only trained, qualified installers, preferably FOA-certified.
a. Installing fiber optics is not difficult, but has special issues
familiar to those with experience
b. Make sure the installers are experienced in the type of installation
you are planning, as installers often specialize in aerial, underwater,
or even singlemode installation
c. Look for FOA
CFOT certification (www.thefoa.org) and good references from
similar installations
d. Review the design with the installer to familiarize them with the
job and see if they have advice on how to make it easier or better but
use your judgement regarding any changes suggested.

4.6.
Install the cable plant. (FOTN, Chapter 15 and NECA-301, Sec 4)
a. NECA 301, Section 5.4 offers good guidelines for installation
b. Watch for proper handling to prevent cable damage, especially cable
tension and bend radius
c. Long lengths (>200m) can be tested by an experienced
technician with an OTDR after installation but before splicing or
termination if there is any question about potential damage during
installation. Remember OTDR testing is optional, but every link
requires insertion loss testing with a meter and source.
d. Install the hardware: NECA 301, Section 5.5
e. Splice as needed: NECA 301, Section 6.3, generally use fusion
splicing in outside plant and singlemode applications, mechanical
splices limited to premises multimode cables
f. Terminate ends: NECA 301, Section 6.2, generally multimode
connectors will be installed on the cables directly while singlemode
connectors will use pre-terminated pigtails to reduce loss and back
reflection which are both important to laser transceivers used with
singlemode fiber, especially in short links (~<2 km)
g. All splices and terminations should be placed in appropriate
hardware for protection
h. Remember to clean
all connectors properly and keep dust caps on all connectors
i. All fiber optic cables should be color-coded by jacket colors
and/or marked with orange or yellow tags or whatever color is
designated for your cable plant to identify it as fiber optic cable.
j. Carefully mark all cables and connections for identification in a
manner consistent with the company documentation processes.
k. Dust caps from the connectors and couplings terminated in the
enclosure belong to that enclosure and should be put in a small plastic
bag and taped inside the cabinet for future use.

a.
All cable plants must be tested for insertion
loss per industry standards (TIA/EIA-526-14 for multimode,
TIA/EIA-526-7 for singlemode fibers) at the wavelength(s) to be used
with the transmission systems chosen
b. Insertion loss must be less than allowable link loss margin for the
communications equipment being used on the fibers
c. Longer cable plants, especially singlemode and those using splices,
should be tested by an experienced technician with an OTDR to verify
splice loss and confirm the cable was not damaged during installation (
Understanding
OTDRs , More
advice on using OTDRs properly.)
d. Remember to clean
all connectors properly and keep dust caps on all connectors
e. All test data should be recorded for cable plant acceptance and
saved for future troubleshooting and restoration

4.8.
Install the communications systems.
a. Install all the active devices according to manufacturer's
specifications and test for proper operation
b. If patchcords are used for connecting optical ports to the cable
plant, use tested patchcords that are known to be in good condition.
Patchcords must match
the fiber in the cable plant being tested to prevent excess
loss.
c. Clean
all connectors after removing dust caps and before connecting
to transceivers or cable plant connectors
d. Using an optical power meter and good reference test cable, test
transmitter power levels to ensure it is within manufacturer's
specifications
e. Using an optical power meter, test receiver power levels to insure
it is within manufacturer's specifications (you can use these two
pieces of data to calculate the loss of the cable plant under actual
use, which should correlate with insertion loss test data using a test
source
f. If the power exceeds the receiver dynamic range and overloads it,
reduce the power by using attenuators of a type recommended by the
equipment manufacturer placed at the receiver, checking with the
optical power meter to ensure the lower power level is in an
appropriate range

4.9.
Document the fiber optic network. (FOTN, Chapter 13 and NECA-301, Sec 8)
a. Perhaps the most important part of any installation is the
documentation. Good documentation is invaluable in upgrading,
troubleshooting or restoring a network
b. Documentation should include:
i. Design data, e.g. CAD drawings and maps
ii. Component types and manufacturers
iii. The paths of each cable
iv. Types of cable (and where the excess is stored for restoration)
v. Cable section lengths
vi. Locations of splices or terminations
vii. Calculated loss budget
viii. The optical loss of each fiber measured at installation
ix. Fiber numbers/colors connected to each communications device,
noting transmitter and receiver orientation
x. Spare fibers available for expansion or use to replaced damaged
fibers
xi. Types of communications equipment
xii. Wavelength of transmission
xiii. Transmitter and receiver power for each transceiver (and
attenuator values if used)
xiv. OTDR traces if taken
xv. Name and contact information for installers
c. Copies of the documentation should be kept at each end of the link
and backups stored in a safe place.

4.10.
Fiber optic premises networks generally do not require periodic
maintenance.
a. As long as the network is communicating as expected, no maintenance
should be required and the network should not be touched unless
communications equipment is moved, added or changed.
b. Attempts at inspection or maintenance are a major cause of damage to
cables or connectors and getting dirt into components
c. Hardware should be lockable to prevent unauthorized entry
d. Outdoor installations, being more prone to mechanical and
environmental damage should be visually inspected for damage as part of
a regularly scheduled preventative maintenance program.

Note: This information is
provided by The Fiber Optic Association, Inc. as a benefit to those
interested in designing, manufacturing, selling, installing or using
fiber optic communications systems or networks. It is intended to be
used as a overview and guideline and in no way should be considered to
be complete or comprehensive. These guidelines are strictly the opinion
of the FOA and the reader is expected to use them as a basis for
creating their own documentation, specifications, etc. The FOA assumes
no liability for their use.